1. Field of the Invention
The present invention relates to a document processing system and more particularly to an automatic system for positively securing a document to a processing device as information is transmitted to or from the document.
2. Prior Art
In all automatic document handling systems, the document must be positively controlled and accurately positioned on the processing device for successful operation. This is particularly true in facsimile transceiver units where information is transmitted from a document to a remote unit which receives the information and prints it onto a receiving document. In these systems, the sending document is fed to a processing device to which the document is removably attached. Operation is normally initiated by the generation of a signal indicating the readiness of a transmitter to transmit a facsimile signal in accordance with the sending document to a remote receiver.
The receiving unit likewise has a processing device to which a blank document is removably secured. The receiver is placed in a ready-to-receive condition, and the processing units of the transmitting and receiving units are operated such that the information from the sending document is transmitted to the receiving document in the receiving unit. Synchronization between the transmitting and receiving units in such a facsimile system is critical and paper position must be accurately and positively set before transmission of information commences and particularly during the transmission.
In several facsimile transceiver systems, the sending and receiving documents are attached to and rotate with a drum. A scan unit traverses the sending document as it is rotated on the drum, and the information read by the scan unit is converted to electrical signals for forwarding to the receiving unit. The receiving unit decodes the signals forwarded from the transmitting unit and through the use of a printer generates on the receiving document the information transmitted from the sending document.
A prior art system for securing the send and receive documents to a processing device is disclosed in U.S. Pat. No. 3,790,159 to Hatzmann, et al., issued Feb. 5, 1974. In this prior art system, a document is fed to a processing drum with a retention member mounted thereon. The retention member includes an arm extending upwardly from the surface of the drum and positioned in the document feed path. A leaf extension is formed from the outer edge of the retention arm and lies above the document feed path when the arm is extended from the drum. As the document is fed into the unit toward the processing drum, the leading edge of the document is positioned under the leaf extension and the retention arm is retracted into the drum to pinch the leading edge of the document between the leaf extension and the drum. In this way, the document is clamped to the drum and aligned relative to the surface of the drum.
While this system has been found to operate satisfactorily, the system does not provide for securing the trailing edge or other portion of the document to the drum. Thus, as the drum and the attached document rotate, the trailing edge of the document may rise from the drum surface thereby interfering with the reading of information from or the printing of information on the document. Additionally, the contact of the free edge with the surrounding structure results in unnecessary noise as well as the emission of paper particules from the document which may clog the printing and other operating elements of the apparatus. This prior art system also requires additional mechanical linkage to operate the movement of the retention arm to grip and release the document processed by the system.